Method of concentrating latex



Patented Mar. 23, 1937 QUNlTED STATES PATENT OFFICE METHOD or CONCENTRATING LATEX British Company No Drawing. Application May 19, 1934, Serial No. 726,570. In Great Britain May 20, 1933 6 Claims.

This invention concerns improvements in or relating to the treatment of rubber latex and in particular concerns the production of concentrated india rubber latex.

The object of the present invention is to im- 5 prove the method of concentrating rubber latex by centrifugal action whereby a more efiective transfer is effected of the rubber globules into the cream fraction.

The invention is not only advantageous in that 1 a greatly increased proportion of the rubber of the original latex is concentrated into the cream, but also in effecting a corresponding reduction with proportionate economy in the quantity of rubber collected in the form of skim.

The present invention can be used in connection with the centrifugal processes described in British Patents Nos. 219,635 and 319,410, and the concentrate produced by the present invention when treated in the customary manner with a latex preservative such as ammonia, can be transported safely for long distances to the industrial country where it will be found to be in a perfect state of preservation.

According to this invention the method of concentrating rubber latex by centrifugal action is characterized by controlling the temperature at which the centrifuging action is performed, by raising the temperature above 45 C. during the centrifugal action of separation and by maintaining or varying the temperature at or between a range of temperature between 45 C. and 85 C.

The concentrate obtained in accordance with this invention may be compounded with one or more of the usual compounding ingredients including filling agents, vulcanizing agents, accelerators, modifiers, and softeners, incorporated in the dry state or in the form of emulsion, and in the latter case the compounded product may be subject to evaporation in order to obtain further concentration of the compounded concentrates.

Example I Two portions drawn from the same bulk of latex are passed through the centrifuge under conditions as closely comparable as possible with the exception of the temperature of the fluid before introduction into the machine. One portion of the latex isat 18 C. (a) and the other at 60 C. (b). The results can be conveniently tabulated as follows:

Temperature of latex 18 C. 60 C. Volume of cream 950 1250 Volume of skim 1150 600 Percentage of rubber in cream 57.0 55.3 Percentage of rubber in skim 28.2 22.7 Percentage of original total solids issuing in the cream 62.6 83.6 Percentage of original total solids issuing in the skim 37.4 16.4

It will be observed that at the higher temperature a considerably greater proportion of the rubber of the original latex is concentrated into the cream and a. considerably smaller proportion of rubber is collected in the form of skim.

Example II In another experiment the results are as follows, and once more demonstrate the advantage of a higher temperature:

Temperature of latex 18C. 60 C. Volume of cream 250 1200 Volume of skim 1600 800 Percentage of rubber in cream 59.6 61.7 Percentage of rubber in skim 21.7 16.4 Percentage of original total solids issuing in the cream 30.0 85.0 Percentage or original total solids issuing in the skim 70.0 15.0

Example III In this case the comparison is made between the degree of separation with the latex introduced at 47 C. and- 77 C. respectively.

What we claim is- 4. A method of concentrating latex which com- 1. The method of concentrating latex which prises centrifugally separating it into cream and comprises raising the temperature above 45 0., skim at a temperature between 45 C. and 85 C. and centrifugally separating the latex into cream 5. The method of concentrating latex which 5 and skim while at a temperature above 45 C. comprises heating the latex and centrifugally sep- 5 2. The method of concentrating latex which arating the latex into cream and. skim while in a comprises maintaining the temperature of the heated condition. latex within a range of temperatures between 6. A method of concentrating latex which com- 45 C. and 85 C., and centrifugal-1y separating prises centrifugally separating it into cream and in it into a cream and a skim while at said temskim at a temperature materially above normal 10 perature. atmospheric temperatures and not above 85 C.

3. The method of concentrating latex according to claim 1 characterized by the addition of DOUGLAS FRANK TWISS.

known compounding ingredients. ERIC WILLIAM BOWER OWEN. 

